Variability of the ITS rDNA and identification of Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae) by rDNA amplification

Abstract

In order to identify the false root-knot nematode, Nacobbus aberrans, a nematode of quarantine importance, investigations were undertaken at the molecular level. Study of the ITS rDNA region among six South American populations showed an extremely high polymorphism. This polymorphism is due to point mutation insertions-deletions, the importance of which is increased by the presence of a degenerate microsatellite in this region. The usefulness of the ITS rDNA is therefore questionable when designing a species-specific identification tool. A study based on partial sequences of the 18S gene was carried out. A conserved part of the 18S gene, with a low level of variation when compared to Pratylenchus spp. and Meloidogyne spp., was found in all the N. aberrans populations tested. The primer set designed for this part of the 18S gene allows the amplification of a 295 bp fragment in all the N. aberrans populations tested. No amplification was obtained with other species belonging to Pratylenchidae, Heteroderidae or Hoplolaimidae. This PCR-based identification tool is effective on all N. aberrans migratory stages. From this study it is concluded that this N. aberrans specific primer set may provide a very useful tool for the identification of South American N. aberrans populations and thereby assist diagnosticians in implementing N. aberrans quarantine regulations.

Obligatory amphimixis and variation in chromosome number within and among South American populations of Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae)

“…In fact, the statistical results support the existence of two separate groups: one group composed of Argentinean, Bolivian and Peruvian populations, and another one composed of one Argentinean population. These results agree with those obtained by molecular approaches with the same populations (Anthoine & Mugniéry, 2005) and also with other population sets (Ibrahim et al, 1997;Reid et al, 2003). Despite their variability, N. aberrans populations grouped according to their geographical origin: South American vs North American populations, except for the Argentinean populations which divide between the two groups.…”

“…Initial material was composed of infected roots. All Nacobbus populations were identified as N. aberrans on the basis of their morphology, according to the description of Sher (1970) and by molecular identification (Anthoine & Mugniéry, 2005). The group of each N. aberrans population was defined, according to the definition of Manzanilla-López et al (2002), by the ability, or not, to develop on bean, chilli pepper, potato, sugar beet and tomato.…”

Top 10 plant‐parasitic nematodes in molecular plant pathology

“…Molecular studies have suggested that N. aberrans sensu Reid et al (2003) is the major species, whereas N. bolivianus (regarded as a synonym of N. aberrans by some authors) is apparently restricted to Bolivia (Castillo et al, 2012). Subsequent studies (Anthoine and Mugniéry, 2005;Lax et al, 2007;Vovlas et al, 2007) have provided molecular evidence to support the existence of at least two major clades within South American Nacobbus. However, a consensus has yet to be achieved on the applicability of molecular diagnostics at species level, and hence most populations and quarantine interceptions will probably still be labelled as N. aberrans sensu Sher, despite mounting evidence to the contrary (Castillo et al, 2012).…”

Éléments de biologie chez Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae): 1 – Capacités de quiescence et de diapause

“…L’étude a été réalisée sur deux populations de N. aberrans : la population N1 originaire de Bolivie (La Paz, Aroma), isolée à partir de racines de pomme de terre et la population N5 originaire d’Argentine isolée à partir de racines de tomate. Ces deux populations ont été identifiées comme N. aberrans selon des critères morphologiques (Sher, 1970), mais aussi par test moléculaire (Anthoine & Mugniéry, 2005a). Elles ont été maintenues sous serre en conditions de confinement S2 sur des plants de tomate ( Lycopersicon esculentum ) var.…”